The present invention relates to the fields of livestock feeds, mammalian poisons and avian poisons, including in particular such feeds and poisons which include effective amounts of materials which are distasteful to avian species.
Certain embodiments of the present invention relate to materials and methods for reducing agricultural losses due to certain avian species, such as starlings. The cost of starlings to an individual farmer from consuming livestock feed can vary considerably from-negligible loss up to several thousand dollars during the fall-winter damage season. Palmer, T. K. 1976, "Pest Bird Damage Control in Cattle Feedlots: The Integrated Systems Approach", Proc. Vertebr. Pest Control Conf., Monterey, Calif. 7:17-21. Generally, the large beef cattle feedlots of the west have the most significant losses. However, moderately sized dairy farms in Tennessee feeding 100 to several hundred head of cattle have been estimated to sustain losses of several hundred dollars during a 3-month damage season. Glahn, J. F., "Blackbird and Starling Depredations at Tennessee Livestock Farms", Proc. Ninth Bird Control Seminar, Bowling Green, Ohio. In Press. Although starlings can be a problem at hog operations, hog producers need not suffer significant feed loss problems with the use and proper adjustment of flip-top feeders and confinement of swine when feeding. In terms of percent feed loss farmers in Tennessee sustained up to 10% loss to birds of the grain component fed to livestock. A similar study in the United Kingdom estimated losses to farmers at up to 12%. Feare, C. J., and K. P. Swannack, "Starling Damage and its Prevention at an Open-Fronted Calf Yard", Anim. Prod. 26:259-265 (1978). Uses of repellents to reduce damage in actual field conditions for protecting costly ($8-12 per hundred weight) high protein feeds from starlings would probably be beneficial if costs of the repellent were below 10% the cost of the feed. This estimate considers only the limited data now available on the maximum cost due to feed loss only. It does not consider other factors such as potential for disease transmission.
The distribution and magnitude of feed loss damage on a national scale has not been studied. However, one study in the winter of 1980 inspected 287 livestock farms in 6 selected livestock producing countries in Tennessee. Glahn, J. F. supra. (In press). Results of this study indicated that 26% of the farms had more than a negligible damage problem including 6% with significant problems where losses exceeding $100 per season would be expected. Based on Tennessee Ag Statistics there were 43,000 hog and dairy farms in Tennessee in 1980. However, since the bird damage survey only sampled farms with greater than 20 head of livestock, the authors estimated the sampled population at 25,900 farms. Therefore, the 6% of the farms that could have benefitted from control measures was 1,554. These data are subject to seasonal changes in bird populations, weather conditions, and farm practices, but gives some idea of the number of farms that might benefit from bird control measures.
Further analysis of the previous data indicated that the primary factors influencing the distribution of damage was the proximity of roosting starlings to the farm, snow cover and mean temperatures below freezing on the day of inspection, and the number of head of livestock on feed. Glahn, J. F., and D. L. Otis, "Factors Influencing the Distribution of Bird Depredations at Livestock Feeding Areas in Tennessee", Bird Damage Research Report No. 231, Denver Wildlife Research Center, Denver, Colo. (1982). Since starlings winter throughout much of the United States, varying degrees of damage at farms is expected depending on winter weather conditions and size of livestock farms, with the most problems occurring at large operations in the northern wintering range of the starling. Although the total number of livestock farms in the U.S. is not readily available, in 1982 Tennessee had 85,000 dairy farms and 23,000 hog farms with 217,000 milk cows and 750,000 hogs compared with national livestock figures of 11 million milk cows and 53 million swine, respectively. The number of beef cattle on feed was not readily available nor was the number of major beef cattle feedlots.
It is extremely difficult to quantify the costs associated in the spread of disease to livestock by starlings essentially because it is difficult to document avian transmission in the first place. Two studies have implicated starlings with spread of transmissible gastroenteritis (TGE) to swine, but no known data exists for other livestock diseases. Gough, P. M., and J. W. Beyer, 1982, "Bird-Vectored Diseases", Proc. Fifth Great Plains Wildlife Damage Control Workshop (R. M. Timm and R. J. Johnson, Eds.), University of Nebraska, Lincoln, Nebr. pp. 260-272; and Pilchard, E. J. 1965, "Experimental Transmission of Transmissible Gastroenteritis Virus by Starlings", J. Vet. Res. 26(114):1177-1179. The costs of TGE may be substantial. For example, during the winter of 1978-79 a TGE outbreak occurring in southeast Nebraska resulted in over 10,000 pigs being lost in one county alone. Because of the possible threat of disease outbreak due to birds, livestock operators and particularly hog producers would be willing to use a material which would keep the birds out of their lots. Whether a feed repellent can do this depends both on the effectiveness of the material and the percent of the feed available to birds that would be treated.
Few objective estimates are available, but in addition to losses from starlings (Sturnus vulgaris), depredation from blackbird (i.e., grackle Quicalus quiscula, red-winged blackbirds Agelaius phoeniceus, and cowbird Molothrus ater) at swine and cattle feedlots is considered a serious economic problem. Besser, J. F. W. C. Royall and J. W. Degrazio, "Baiting Starlings with DRC-1339 at a Cattle Feedlot", J. Wildl. Manage., 31:48-51 (1967); Besser, J. F. J. W. DeGrazio and J. L. Guarino, "Costs of Wintering Starlings and Red-Winged Blackbirds at Feedlots", J. Wildl. Manage. 32:179-180 (1968); Feare, C. J., "Cost of Starling Damage of an Intensive Husbandry Unit", Proc. British Insecticide and Fungicide Conf. 8:253-259 (1975); Feare, C. J. (1980), "The Economies of Starling Damage", Econ. of Dam. 2:39-54; Stickley, A. R., "Extended Use of Starlicide in Reducing Bird Damage in Southeastern Feedlots", Proc. Bird. Cont. Sem. 8:79-89 (1979); and Twedt, D. J. and J. F. Glahn, " Reducing Starling Depredations at Livestock Feeding Operations Through Changes in Management Practices", Proc. Vertebr. Pest. Conf. 10:159-163 (1982). Losses may result from feed contamination and disease transmission, or from feed consumption, and problems are exacerbated when complete diets are presented in open troughs to which birds have access. See Russell, H. G., "Blackbird Control at Two Army Installations: Environmental Impact Statement", Office Chief Eng., Directorate Facilities Eng., Washington, D.C. (1975); Twedt D. J. and J. F. Glahn supra. (1982) and Rickaby, C. D., "A Review of the Nutritional Aspects of Complete Diets for Dairy Cows", ADAS Q. Rev., 29:51-76 (1978). In that situation, up to 9% of the high protein fraction of the diet can be taken, thus depriving livestock of their high value nutrient source and altering the composition of the entire ration. Feare, C. J. and J. T. Wadsworth, "Starling Damage on Farms Using the Complete Diet System of Feeding Dairy Cows", Anim. Prod. 32:179-183 (1981). Efforts to control problem birds at feedlots mainly have involved trapping and/or the use of lethal chemical agents. See Besser, J. F., W. C. Royall and J. W. DeGrazio supra. (1967); Bogadich, V., "The Use of Live Traps to Remove Starlings and Protect Agricultural Products", Proc. Vertebr. Pest. Conf. 3:98-99 (1968); Levingston, P. E., "Winter Starling Control with DRC-1339. " Proc. Vertebr. Pest. Conf. 3:100-103 (1967); West, R. R., J. F. Besser and J. W. DeGrazio., "Starling Control in Livestock
Feeding Areas", Proc. Vertebr. Pest. Conf. 3:89-93 (1967); and Feare, C. J. and J. T. Wadsworth, supra. (1981). These approaches fail to create a sub-optimal environment for avian feeding activity, however, and the birds rapidly reinfest feedlots when control measures are relaxed. See Twedt, D. J. and J. F. Glahn, supra. (1982). Additional problems arise when lethal chemicals such as starlicide (1% C-chloro-p-toludine hydrochloride on poultry pellets) are used, including primary and secondary hazards to non-target animals, development of bait aversion by target birds, and increased expense and labor in prebaiting, baiting and monitoring. See Cunningham, D. J., E. W. Schafer and L. K. McConnell, "DRC-1339 and DRC-2698 Residues in Starlings: Preliminary Evaluation of Their Effects on Secondary Hazard Potential", Proc. Bird Contr. Sem. 8:31-37 (1979); and Glahn, J. F., "Use of Starlicide to Reduce Starling Damage at Livestock Feeding Operations", Proc. Great Plains Wildl. Dam. Wrkshp. 5:273-277 (1981). Twedt and Glahn outlined management practices that could be implemented at feedlots to substantially reduce bird depredation. Twedt, D. J. and J. F. Glahn, supra. (1982) Among the suggested practices was the use of feeds that are either unpalatable or that cannot be metabolized by birds. In the latter case, relatively high levels of non-protein nitrogen (e.g., urea) and/or alfalfa might be added. In the former case, certain tastants might be used. Compounds do exist that are unpalatable to birds but readily accepted by mammals. See Welty, J. C., "The Life of Birds", W. B. Saunders Book Co., Philadelphia, Pa., at page 72 (1975).
One compound unpalatable to avian species is dimethyl anthranilate (DMA), non-toxic food flavoring approved for human consumption, but offensive to birds, even when presented at low concentrations. DMA has been suggested as a compound to reduce consumption of normally preferred foods by birds. See U.S. Pat. No. 2,967,128 (Kare). The Kare patent also discloses that certain compounds, particularly esters of anthranilic acid, esters of phenylacetic acid and dimethyl benzyl carbonyl acetate, are organic compounds which may be used to treat bird edibles in solution, suspension, emulsion or "other type of formulation". The most effective of the compounds disclosed in this patent is dimethyl anthranilate (methyl ortho-N-methylamino benzoate). Although U.S. Pat. No. 2,967,128 discloses that dimethyl anthranilate "has very excellent repellent action for prolonged periods and very small concentrations", subsequent testing has found that, when used outdoors, dimethyl anthranilate quickly loses its efficacy (see FIG. 1 of this application). Applicants hereto have theorized that the rapid loss of persistency under field conditions may result in part from photochemical decomposition of the dimethyl anthranilate to degradation products which exhibit little or no taste activity, and/or to the simple evaporation of those materials. Accordingly dimethyl anthranilate has not been widely used commercially since its discovery about a quarter of a century ago.
In addition to the problems encountered in preventing loss of mammalian livestock feeds to avian species, other problems stem from the unwanted ingestion of materials intended for consumption by mammalian species. For example, rodenticides and insecticides are often consumed by avian species. If they are not killed, they may concentrate lethal agents in such quantities as to cause the secondary poisoning of their predators. Since many of these predators are endangered species, a method of preventing avian prey from ingesting such substances should reduce the incidence of secondary poisonings. See Balcomb, R., "Secondary Poisoning of Red Shouldered Hawks With Carbonfuran", J. Wildl. Manage. 47(4);1089-1132 (1983).
In another context, it is often desired to poison and kill certain avian species, such as starlings. Presently, complete starlicides are available which comprise discrete poison and food components. In theory, starlings will, in the process of eating the presented food, consume a lethal amount of the presented poisons. Unfortunately, some starlings can effectively distinguish between the poisoned and unadulterated food, such that they avoid consuming lethal amounts of former. Accordingly, a need exists for an improved complete avian poison, such as a complete starlicide, which does not suffer fro these drawbacks.